The present invention relates to a catheter inserter, that is, a device for inserting a catheter into the human body. Catheters have long been utilized in the medical profession and are designed for insertion into blood vessels and similar passageways or cavities in the body, to permit injection or withdrawal of fluids or to maintain the openness of an existing passageway into the existing vessel or cavity for subsequent injection or withdrawal of fluids. Various devices have been used for the insertion of catheters. All such devices have, in common, the use of a cannula, in order to make the original opening into the vessel or cavity. The catheter is normally mounted on the cannula and, when the cannula has pierced the vessel or cavity, the catheter is moved into position so as to maintain the opening when the cannula is withdrawn, and the cannula is thereafter withdrawn. Recently, it has become particularly desirable in order to avoid the spread of infection to ensure that the cannula, when withdrawn, is not exposed to prevent the cannula tip from piercing the flesh of the user or third parties during disposal.